Hooray, you got it!
These Harts are "Demon-like" because the Hawker Demon was a fighter-plane variant, developed from the Hawker Hart, and very similar in appearance and design. (The Hawker Hind and Hawker Fury suggested by my clue were also similar planes based on the same design.) Arguably slightly obscure knowledge, though Googling the words Hart and Demon would take you quite quickly to the necessary Wikipedia page. And they were famous planes in their day, direct forerunners to the monoplane design of the Hawker Hurricane.
This Wikipedia page will give you all the info you need on this family of aircraft, I think.
The word "accomplishes" in my question, was a hinting reference to the returning pilot's phrase: "Mission acomplished" after they think they've shot Tintin down. (As I said, I'm not sure if anything like the word accomplish is said there in the French original.)
Anyway, a well-earned and much-toiled-for point for yamilah, scorekeeper!